The invention relates to the field of probe card assembly systems. More particularly, the invention relates to improvements in photolithography-patterned spring contacts and enhanced probe card assemblies having photolithography-patterned spring contacts for use in the testing or burn-in of integrated circuits.
In conventional integrated circuit (IC) wafer probe cards, electrical contacts between the probe card and an integrated circuit wafer are typically provided by tungsten needle probes. However, advanced semiconductor technologies often require higher pin counts, smaller pad pitches, and higher clock frequencies, which are not possible with, tungsten needle probes.
While emerging technologies have provided spring probes for different probing applications, most probes have inherent limitations, such as limited pitch, limited pin count, varying levels of flexibility, limited probe tip geometries, limitations of materials, and high costs of fabrication.
K. Banerji, A. Suppelsa, and W. Mullen III, Selectively Releasing Conductive Runner and Substrate Assembly Having Non-Planar Areas, U.S. Pat. No. 5,166,774 (24 Nov. 1992) disclose a runner and substrate assembly which comprises xe2x80x9ca plurality of conductive runners adhered to a substrate, a portion of at least some of the conductive runners have non-planar areas with the substrate for selectively releasing the conductive runner from the substrate when subjected to a predetermined stressxe2x80x9d.
A. Suppelsa, W. Mullen III and G. Urbish, Selectively Releasing Conductive Runner and Substrate Assembly, U.S. Pat. No. 5,280,139 (18 Jan. 1994) disclose a runner and substrate assembly which comprises xe2x80x9ca plurality of conductive runners adhered to a substrate, a portion of at least some of the conductive runners have a lower adhesion to the substrate for selectively releasing the conductive runner from the substrate when subjected to a predetermined stressxe2x80x9d.
D. Pedder, Bare Die Testing, U.S. Pat. No. 5,786,701 (28 Jul. 1998) disclose a testing apparatus for testing integrated circuits (ICs) at the bare die stage, which includes xe2x80x9ca testing station at which microbumps of conductive material are located on interconnection trace terminations of a multilayer interconnection structure, these terminations being distributed in a pattern corresponding to the pattern of contact pads on the die to be tested. To facilitate testing of the die before separation from a wafer using the microbumps, the other connections provided to and from the interconnection structure have a low profilexe2x80x9d.
D. Grabbe, I. Korsunsky and R. Ringler, Surface Mount Electrical Connector, U.S. Pat. No. 5,152,695 (06 Oct. 1992) disclose a connector for electrically connecting a circuit between electronic devices, in which xe2x80x9cthe connector includes a platform with cantilevered spring arms extending obliquely outwardly therefrom. The spring arms include raised contact surfaces and in one embodiment, the geometry of the arms provide compound wipe during deflectionxe2x80x9d.
H. Iwasaki, H. Matsunaga, and T. Ohkubo, Partly Replaceable Device for Testing a Multi-Contact Integrated Circuit Chip Package, U.S. Pat. No. 5,847,572 (08 Dec. 1998) disclose xe2x80x9ca test device for testing an integrated circuit (IC) chip having side edge portions each provided with a set of lead pins. The test device comprises a socket base, contact units each including a contact support member and socket contact numbers, and anisotropic conductive sheet assemblies each including an elastic insulation sheet and conductive members. The anisotropic conductive sheet assemblies are arranged to hold each conductive member in contact with one of the socket contact members of the contact units. The test device further comprises a contact retainer detachably mounted on the socket base to bring the socket contact members into contact with the anisotropic sheet assemblies to establish electrical communication between the socket contact members and the conductive members of the anisotropic conductive sheet assemblies. Each of the contact units can be replaced by a new contact unit if the socket contact members partly become fatigued, thereby making it possible to facilitate the maintenance of the test device. Furthermore, the lead pins of the IC chip can be electrically connected to a test circuit board with the shortest paths formed by part of the socket contact members and the conductive members of the anisotropic conductive sheet assembliesxe2x80x9d.
W. Berg, Method of Mounting a Substrate Structure to a Circuit Board, U.S. Pat. No. 4,758,9278 (19 Jul. 1988) discloses xe2x80x9ca substrate structure having contact pads is mounted to a circuit board which has pads of conductive material exposed at one main face of the board and has registration features which are in predetermined positions relative to the contact pads of the circuit board. The substrate structure is provided with leads which are electrically connected to the contact pads of the substrate structure and project from the substrate structure in cantilever fashion. A registration element has a plate portion and also has registration features which are distributed about the plate portion and are engageable with the registration features of the circuit board, and when so engaged, maintain the registration element against movement parallel to the general plane of the circuit board. The substrate structure is attached to the plate portion of the registration element so that the leads are in predetermined position relative to the registration features of the circuit board, and in this position of the registration element the leads of the substrate structure overlie the contact pads of the circuit board. A clamp member maintains the leads in electrically conductive pressure contact with the contact pads of the circuit boardxe2x80x9d.
D. Sarma, P. Palanisamy, J. Hearn and D. Schwarz, Controlled Adhesion Conductor, U.S. Pat. No. 5,121,298 (09 Jun. 1992) disclose xe2x80x9cCompositions useful for printing controllable adhesion conductive patterns on a printed circuit board include finely divided copper powder, a screening agent and a binder. The binder is designed to provide controllable adhesion of the copper layer formed after sintering to the substrate, so that the layer can lift off the substrate in response to thermal stress. Additionally, the binder serves to promote good cohesion between the copper particles to provide good mechanical strength to the copper layer so that it can tolerate lift off without fracturexe2x80x9d.
R. Mueller, Thin-Film Electrothermal Device, U.S. Pat. No. 4,423,401 (27 Dec. 1983) discloses xe2x80x9cA thin film multilayer technology is used to build micro-miniature electromechanical switches having low resistance metal-to-metal contacts and distinct on-off characteristics. The switches, which are electrothermally activated, are fabricated on conventional hybrid circuit substrates using processes compatible with those employed to produce thin-film circuits. In a preferred form, such a switch includes a cantilever actuator member comprising a resiliently bendable strip of a hard insulating material (e.g. silicon nitride) to which a metal (e.g. nickel) heating element is bonded. The free end of the cantilever member carries a metal contact, which is moved onto (or out of) engagement with an underlying fixed contact by controlled bending of the member via electrical current applied to the heating elementxe2x80x9d.
S. Ibrahim and J. Elsner, Multi-Layer Ceramic Package, U.S. Pat. No. 4,320,438 (16 Mar. 1982) disclose xe2x80x9cIn a multi-layer package, a plurality of ceramic lamina each has a conductive pattern, and there is an internal cavity of the package within which is bonded a chip or a plurality of chips interconnected to form a chip array. The chip or chip array is connected through short wire bonds at varying lamina levels to metallized conductive patterns thereon, each lamina level having a particular conductive pattern. The conductive patterns on the respective lamina layers are interconnected either by tunneled through openings filled with metallized material, or by edge formed metallizations so that the conductive patterns ultimately connect to a number of pads at the undersurface of the ceramic package mounted. onto a metalized board. There is achieved a high component density; but because connecting leads are xe2x80x9cstaggeredxe2x80x9d or connected at alternating points with wholly different package levels, it is possible to maintain a 10 mil spacing and 10 mil size of the wire bond lands. As a result, there is even greater component density but without interference of wire bonds one with the other, this factor of interference being the previous limiting factor in achieving high component density networks in a multi-layer ceramic packagexe2x80x9d.
F. McQuade, and J. Lander, Probe Assembly for Testing Integrated Circuits, U.S. Pat. No. 5,416,429 (16 May 1995) disclose a probe assembly for testing an integrated circuit, which xe2x80x9cincludes a probe card of insulating material with a central opening, a rectangular frame with a smaller opening attached to the probe card, four separate probe wings each comprising a flexible laminated member having a conductive ground plane sheet, an adhesive dielectric film adhered to the ground plane, and probe wing traces of spring alloy copper on the dielectric film. Each probe wing has a cantilevered leaf spring portion extending into the central opening and terminates in a group of aligned individual probe fingers provided by respective terminating ends of said probe wing traces. The probe fingers have tips disposed substantially along a straight line and are spaced to correspond to the spacing of respective contact pads along the edge of an IC being tested. Four spring clamps each have a cantilevered portion which contact the leaf spring portion of a respective probe wing, so as to provide an adjustable restraint for one of the leaf spring portions. There are four separate spring clamp adjusting means for separately adjusting the pressure restraints exercised by each of the spring clamps on its respective probe wing. The separate spring clamp adjusting means comprise spring biased platforms each attached to the frame member by three screws and spring washers so that the spring clamps may be moved and oriented in any desired direction to achieve alignment of the position of the probe finger bps on each probe wingxe2x80x9d.
D. Pedder, Structure for Testing Bare Integrated Circuit Devices, European Patent Application No. EP 0 731 369 A2 (Filed 14 Feb. 1996), U.S. Pat. No. 5,764,070 (09 Jun. 1998) discloses a test probe structure for making connections to a bare IC or a wafer to be tested, which comprises xe2x80x9ca multilayer printed circuit probe arm which carries at its tip an MCM-D type substrate having a row of microbumps on its underside to make the required connections. The probe arm is supported at a shallow angle to the surface of the device or wafer, and the MCM-D type substrate is formed with the necessary passive components to interface with the device under test. Four such probe arms may be provided, one on each side of the device under testxe2x80x9d.
B. Eldridge, G. Grube, I. Khandros, and G.. Mathieu, Method of Mounting Resilient Contact Structure to Semiconductor Devices, U.S. Pat. No. 5,829,128 (03 Nov. 1998), Method of Making Temporary Connections Between Electronic Components, U.S. Pat. No. 5,832,601 (10 Nov. 1998), Method of Making Contact Tip Structures, U.S. Pat. No. 5,864,946 (02 Feb. 1999), Mounting Spring Elements on Semiconductor Devices, U.S. Pat. No. 5,884,398 (23 Mar. 1999), Method of Burning-In Semiconductor Devices, U.S. Pat. No. 5,878,486 (9 Mar. 1999), and Method of Exercising Semiconductor Devices, U.S. Pat. No. 5,897,326 (27 Apr. 1999), disclose xe2x80x9cResilient contact structures are mounted directly to bond pads on semiconductor dies, prior to the dies being singulated (separated) from a semiconductor wafer. This enables the semiconductor dies to be exercised (e.g. tested and/or burned-in) by connecting to the semiconductor dies with a circuit board or the like having a plurality of terminals disposed on a surface thereof. Subsequently, the semiconductor dies may be singulated from the semiconductor wafer, whereupon the same resilient contact structures can be used to effect interconnections between the semiconductor dies and other electronic components (such a wiring substrates, semiconductor packages, etc.). Using the all-metallic composite; interconnection elements of the present invention as the resilient contact structures, burn-in can be performed at temperatures of at least 150xc2x0 C., and can be completed in less than 60 minutesxe2x80x9d. While the contact tip structures disclosed by B. Eldridge et al. provide resilient contact structures, the structures are each individually mounted onto bond pads on semiconductor dies, requiring complex and costly fabrication. As well, the contact tip structures are fabricated from wire, which often limits the resulting geometry for the tips of the contacts. Furthermore, such contact tip structures have not been able to meet the needs of small pitch applications (e.g. typically on the order of 50 xcexcm spacing for a peripheral probe card, or on the order of 75 xcexcm spacing for an area array).
T. Dozier II, B. Eldridge, G. Grube, I. Khandros, and G. Mathieu, Sockets for Electronic Components and Methods of Connecting to Electronic Components, U.S. Pat. No. 5,772,451 (30 Jun. 1998) disclose xe2x80x9cSurface-mount, solder-down sockets permit electronic components such as semiconductor packages to be releasably mounted to a circuit board. Resilient contact structures extend from a top surface of a support substrate, and solder-ball (or other suitable) contact structures are disposed on a bottom surface of the support substrate. Composite interconnection elements are used as the resilient contact structures disposed atop the support substrate. In any suitable manner, selected ones of the resilient contact structures atop the support substrate are connected, via the support substrate, to corresponding ones of the contact structures on the bottom surface of the support substrate. In an embodiment intended to receive an LGA-type semiconductor package, pressure contact is made between the resilient contact structures and external connection points of the semiconductor package with a contact force which is generally normal to the top surface of the support substrate. In an embodiment intended to receive a BGA-type semiconductor package, pressure contact is made between the resilient contact structures and external connection points of the semiconductor package with a contact force which is generally parallel to the top surface of the support substratexe2x80x9d.
Other emerging technologies have disclosed probe tips on springs which are fabricated in batch mode processes, such as by thin-film or micro electronic mechanical system (MEMS) processes.
D. Smith and S. Alimonda, Photolithographically Patterned Spring Contact, U.S. Pat. No. 5,613,861 (25 Mar. 1997), U.S. Pat. No. 5,848,685 (15 Dec. 1998), and International Patent Application No. PCT/US 96/08018 (Filed 30 May 1996), disclose a photolithography patterned spring contact, which is xe2x80x9cformed on a substrate and electrically connects contact pads on two devices. The spring contact also compensates for thermal and mechanical variations and other environmental factors. An inherent stress gradient in the spring contact causes a free portion of the spring to bend up and away from the substrate. An anchor portion remains fixed to the substrate and is electrically connected to a first contact pad on the substrate. The spring contact is made of an elastic material and the free portion compliantly contacts a second contact pad, thereby contacting the two contact padsxe2x80x9d. While the photolithography patterned springs, as disclosed by Smith et al., are capable of satisfying many IC probing needs, the springs are small, and provide little vertical compliance to handle the planarity compliance needed in the reliable operation of many current IC prober systems. Vertical compliance for many probing systems is typically on the order of 0.004xe2x80x3-0.010xe2x80x3, which often requires the use of tungsten needle probes.
Furthermore, no one has taught a way to interconnect such a probe containing up to several thousand pins to a tester, while effectively dealing with planarity requirements. As advanced integrated circuit devices become more complex while decreasing in size, it would be advantageous to provide a probe card assembly which can be used to reliably interconnect to such devices.
To accommodate for planarity differences between an array of probe tips and the surface pads on a wafer under test, it may be advantageous to provide a probe substrate which can pivot freely by a small amount about its center. For such a system, however, an accurately controlled force must still be provided to engage the contacts, while holding the substrate positionally stable in the X, Y, and theta directions. Furthermore, for applications in which the substrate includes a large number (e.g. thousands) of wires or signals exiting its backside, wherein supports are located at the periphery of the substrate, these supports must not hinder the fan-out exit pathways. As well, the signal wires must not hinder the pivoting of the substrate, nor should they hinder the controlled force provided to engage the springs against a device under test (DUT).
It would be advantageous to provide a method and apparatus for improved flexible probe springs, which are capable of high pin counts, small pitches, cost-effective fabrication, and customizable spring tips. It would also be advantageous to provide probe card assemblies using such flexible probe springs, which provide planarity compliance to semiconductor devices under testing and/or burn-in, while providing accurate axial and theta positioning.
Several embodiments of integrated circuit probe card assemblies are disclosed, which extend the mechanical compliance of both MEMS and thin-film fabricated probes, such that these types of spring probe structures can be used to test one or more integrated circuits on a semiconductor wafer. Several embodiments of probe card assemblies are disclosed, which provide tight signal pad pitch and compliance, preferably enabling the parallel testing or burn-in of multiple ICs, using commercial wafer probing equipment. In some preferred embodiments, the probe card assembly structures include separable standard electrical connector components, which reduces assembly manufacturing cost and manufacturing time. These structures and assemblies enable high speed testing of IC""s in wafer form, as well as, high density substrates. The probes preferably include mechanical protection for both the integrated circuits and the MEMS or thin film fabricated spring tips. Interleaved spring probe tip designs are defined which allow multiple probe contacts on very small integrated circuit pads. The shapes of probe tips are preferably defined to control the depth of probe tip penetration between a probe spring and a pad or trace on an integrated circuit device. Improved protective coating techniques for spring probes are also disclosed, offering increased quality and extended useful service lives for probe card assemblies.